~17 Liberal-Unionist MPs (Conscription Crisis)

The Conscription Crisis of 1917 shattered the Liberal Party along linguistic and regional lines. When Prime Minister Robert Borden introduced the Military Service Act to impose compulsory military service for World War I, approximately 17 English-speaking Liberal MPs broke with party leader Wilfrid Laurier to support conscription and join Borden's Union Government. These included prominent figures such as Hugh Guthrie, William Stevens Fielding, Frank Broadstreet Carvell (who became Minister of Public Works), Alexander Kenneth Maclean, William Stewart Loggie, Frederick Forsyth Pardee, Edward Walter Nesbitt, Thomas MacNutt, Levi Thomson, Hugh Havelock McLean, James McCrie Douglas, William Andrew Charlton, William Ashbury Buchanan, Robert Lorne Richardson, and Michael Clark. The split was fundamentally about the war effort: these MPs believed that voluntary enlistment had failed and conscription was necessary to reinforce the Canadian Expeditionary Force in the trenches of France and Belgium.

The Union Government won a landslide victory in the December 1917 election, carrying every province except Quebec. However, the conscription crisis left deep scars. The Liberal Party was devastated in English Canada while the Conservatives were virtually eliminated in Quebec — a political realignment that persisted for decades. Many of the Liberal-Unionists never returned to the Liberal fold; some joined the nascent Progressive movement of the 1920s, others drifted to the Conservatives. Fielding eventually returned to the Liberals and served as Mackenzie King's Minister of Finance in 1921. Carvell was appointed to the Railway Commission. The crisis permanently altered Canadian politics, reinforcing the fundamental tension between English and French Canada over military obligations to the British Empire.